The present invention relates to a treatment method for diamonds to improve the crystallinity of diamonds used as semiconductors and insulating materials in the electronics industry.
Diamonds have attracted interest recently as semiconductors and insulating materials in the electronics industry due to many excellent properties thereof. However, artificial diamonds generally tend to contain lattice defects and non-diamond components such as graphite and the like.
For instance, in the case of a diamond thin film deposited on a substrate material by the CVD (Chemical Vapor Deposition) method, the diamond is under a metastable state in an ambient (i.e., an environment or atmosphere) wherein the CVD is performed, and graphite and other non-crystalline carbon components having more stability get sometimes into the diamond thin film. Also, when ions of such elements as boron and the like are irradiated on a diamond to make it electro-conductive, it is known that lattice defects and non-diamond components will be created due to the ion implantation in the region where the ions are implanted.
These lattice defects and non-diamond components cause the excellent features of the diamond in the electrical characteristics such as insulating resistivity, carrier mobility and the like, and also in the mechanical characteristics, for example, to deteriorate greatly.
In order to make the most of the inherent features of the diamond, it is necessary to restore the intrinsic diamond structure in the region suffering from the lattice defects and non-diamond components or to remove the causes that have resulted in deterioration of the features of the diamond.
As explained in the foregoing, it is necessary to apply a treatment to diamonds for elimination of the adverse effects as enumerated above in order to use the diamond widely in the industry.
The measures so far employed for the above purpose only find a method of thermal annealing, a method of chemical etching wherein immersing in a mixed solution of nitric acid and sulfuric acid takes place or an etching method performed through an exposure to argon plasma.
The aforementioned thermal annealing method is to try to recover the crystal lattice by supplying energy through heating a specimen as often practiced with silicon. However, in the case of diamonds, heat application tends to produce graphite and the treatment method by annealing can not possibly contribute to elimination of the lattice defects very much.
The etching in a mixed solution of nitric acid and sulfuric acid can remove the non-diamond components existing on the surface, but it is difficult to remove the lattice defects and the non-diamond components contained within the crystal. Besides, the substrate materials that can be treated according to this method are limited in variety.
Furthermore, the etching treatment by plasma has shown a problem of inflicting additional damages on account of a bombardment of the high energy ions and electrons contained in the plasma.
Thus, the treatment methods that have been so far practiced are not good enough and a new treatment method for diamonds has been much sought after.